transparent (test) grid showing up when rendering?
The rendered scene you posted seems to be from an earlier version of your blend file than the one you posted. When I render using the blend file you posted, I don't have any transparency problems:



Try rendering again and see if you still have the problem. 

One thing about your file I noticed is that on frame 1, the camera itself is positioned partially inside the wall:



The part circled in green is where the camera sees from, not from the front, shown here in red:



That results in your scene at frame 1 of your animation being partially obscured by the wall, like this:



To fix this, simply move the camera at frame 1 fully into the room, then set a keyframe for it: